Four Pillars of Destiny (Bazi)

The Four Pillars of Destiny is known as 'eight characters of birth time', namely Sheng Chen Ba Zi, shortly as Bazi in Pinyin. As an important component of Chinese fortune telling, the 'four pillars' refers to the year, month, day and hour pillars of a birthday in Chinese solar calendar and each pillar has two characters, eight characters (Ba Zi) in total. Two characters in each pair are made up of one character from the Heavenly Stems and one from the Earthly Branches. 

The theory of the Chinese Four Pillars of Destiny is based on Yin Yang and Wu Xing, and the pillars are represented on the basis of the heavenly stems & earthly branches. 
 

– Ten Heavenly Stems and Twelve Earthly branches combines and create a sexagenary cycle (See this chart to find the year pillar. If your birth year is not in the 60-year circle, it can be calculated by extrapolation from the figures.) Here is a quick way to convert a year in western calendar into the one represented by stem and branch. 

Year's Heavenly Stem – Last number of a year will indicate the year's stem

Jia	Yi	Bing	Ding	Wu	Ji	Geng	Xin	Ren	Gui
4	5	6	7	8	9	0	1	2	3

Year's Earthly Branch – the reminder (1-11) of the year divided by 12 will indicate the year's branch

Zi	Chou	Yin	Mao	Chen	Si	Wu	Wei	Shen	You	Xu	Hai
4	5	6	7	8	9	10	11	0	1	2	3

Take the year 1985 for example. Last number 5 refers to Yi. 1985 divided by 12 equals an integer 165 with a reminder of 5. Number 5 refers to Chou. So 1985 is Yi Chou year.
 

– Month pillar has fixed early branches, lunar January to October represented by Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai, Zi and Chou. The heavenly stem is changing according to the year pillar. In fact, the division of two month branches is usually up to the 24 solar terms. From the Beginning of Spring which regarded as the real start of a year, the branch shifts every two solar terms. The representation by lunar months is only an only an approximation.

Earthly Branches and 12 Months

Branch	Zi	Chou	Yin	Mao	Chen	Si
Lunar	Nov.	Dec.	Jan.	Feb.	Mar.	Apr.
Solar	Daxue- Xiaohan	Xiaohan- Lichun	Lichun- Jingzhe	Jingzhe- Qingming	Qingming- Lixia	Lixia- Mangzhong
Branch	Wu	Wei	Shen	You	Xu	Hai
Lunar	May	Jun.	Jul.	Aug.	Sep.	Oct.
Solar	Mangzhou- Xiaoshu	Xiaoshu- Liqiu	Liqiu- Bailu	Bailu- Hanlu	Hanlu- Lidong	Lidong- Daxue

 – The recondition to know a day's stem and branch, one should remember the stem and branch of the first day of that year in Chinese lunar calendar. Then, Chinese calendar has bigger and lesser month, respectively having 30 or 29 days. One stem-branch cycle needs 60 days. If the stem and branch of the first day of that lunar month has been known, there is a way to extrapolate any day within the month, by the different extrapolation rules applied to bigger and lesser months. 
 – Similarly, the heavenly branches of the hour pillar is fixed. Jia hour refers to 23:00-01:00, and so forth. The heavenly stem of each day is up to the stem and branch of the day pillar. 

Earthly Branches of 24 Hours (12 Shi Chen)

Zi	Chou	Yin	Mao	Chen	Si
23:00-00:59	01:00-02:59	03:00-04:59	05:00-06:59	07:00-08:59	09:00-10:59
Wu	Wei	Shen	You	Xu	Hai
11:00-12:59	13:00-14:59	15:00-16:59	17:00-18:59	19:00-20:59	21:00-22:59

 Here is the Bazi chart interpretation for an individual born at 18:00, on April 12, 1985 (lunar February 23, 1985) in western calendar for example. Generally, a yellow calendar book is necessary to help find the accurate pillars. Now, it is very easy to find an online Ba Zi calculator. 

 

Pillars	Hour	Day	Month	Year
Heavenly Stems	Ding	Ding	Geng	Yi
Wu Xing/Yin Yang	Yin Fire	Yin Fire	Yang Metal	Yin Wood
Earthly Branches	You	Chou	Chen	Chou
Wu Xing/Yin Yang	Yin Metal	Yin Earth	Yang Earth	Yin Earth

It has only eight characters, but the relation of the eight characters is very complicated. According to the Bazi analysis theory, year pillar represents ancestors and parents; month pillar represents brothers and sisters; day stem represents oneself; day branch represent spouse; hour pillar represents offspring. In addition, the heavenly stems have their own characteristics which are related to the Five Elements (Wu Xing). The missing element in a baby's Bazi will be usually added into its name as an action of compensation. Among the ten heavenly stems, there are compatible and opposite relations. While among the earthly branches, the relations are more complex, combination, clash, restriction, harm, etc. Abundant relationships may have accurate explanation on the luck of one self or relatives. 

The ancient people believed that birth time is a kind of Qi (aura, something of spirit). People born in the Wei hour have an aura field of Wei. If the birth time is in Wei hour but closing to Shen, the aura field has changed gradually to that of the Shen hour. The Four Pillars of Destiny was created based on vague time, as the time division in ancient time could not be accurate as it is in modern times. So, are there any errors if calculating the Ba Zi because of the time difference? An individual is unique replying on the combination of time, space and spirit. While the Four Pillars mainly talks about time, occasionally space but non spirit. It is an outcome of Chinese metaphysics which is special, interesting but the accurate is debatable.